Hydrophilized bactericidal polymers

ABSTRACT

A bactericidal polymeric composition includes a hydrophilic first comonomer copolymerized to a second comonomer to produce a polymeric composition that is more hydrophilic or more bactericidal in an aqueous solution than either of the comonomers alone. Methods for identifying bactericidal polymers, methods for rendering materials bactericidal, and methods for using bactericidal compositions to kill or reduce bacterial growth are also described. Applications for the inventive compositions include their use in catheters, stents, medical devices, contact lenses; root canal fillers; and/or wound dressings.

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Application No. 60/711,234, filed Aug. 24, 2005,which is hereby incorporated by reference in its entirety.

BACKGROUND

There is an ever-growing demand for materials suitable for killingharmful microorganisms. Such materials could be used to coat surfaces ofcommon objects touched by people to render them antiseptic so as toprevent transmission of bacterial infections or to facilitate thekilling of microorganisms in solution.

Various polycations are known to have bactericidal properties. However,their bactericidal properties can be strongly influenced by whether thepolycation or a composition containing the polycation is soluble. Insome instances the bactericidal property is most apparent in aninsoluble form, which is not particularly amenable to killingmicroorganisms. In other instances the bactericidal activity is lostwhen the polycation is cross-linked or otherwise rendered insoluble.Application of bactericidal polymers may also be limited by their use inbrushes, their insolubility in solution, or by their unfavorablebiocompatibility characteristics. Accordingly, there is a need forbactericidal formulations possessing having improved bactericidal,hydrophilicity/wettability and biocompatibility characteristics suitablefor rendering materials or areas bactericidal and for killing airborneand/or waterborne microorganisms.

BRIEF SUMMARY

The present invention is directed to polymeric compositions providingimproved bactericidal, hydrophilicity/wettability, and biocompatibilitycharacteristics. In particular, the present invention provides abactericidal composition, including a hydrophilic first comonomerpolymerized to a second comonomer to form a polymeric composition, wherethe polymeric composition is more soluble and/or more bactericidal in anaqueous solution than either of the first comonomer or the secondcomonomer alone.

In a particular example, the present invention provides a quaternizedbactericidal composition, in which poly(4-vinylpyridine) (PVP) iscopolymerized with hydroxyethylmethacrylate (HEMA) orpoly(ethyleneglycol) methacrylate (PEGMA).

In another example, the present invention provides a method forrendering a material or area bactericidal in which a bactericidalcomposition of the present invention is applied to a medium or device inan amount suitable for killing or significantly reducing the number ofbacteria in or on the treated medium or device compared to an untreatedmedium or device.

In another example, the present invention provides a method for killingor significantly reducing the number of bacteria on a material or areatreated with a bactericidal composition of the present invention.

In a further example, the present invention provides a method foridentifying a polymer having suitable bactericidal activity in which ahydrophilic first comonomer is polymerized to a second comonomer to forma bactericidal polymeric composition, where the polymeric composition isdetermined to have suitable bactericidal activity if the polymericcomposition has a higher bactericidal activity in an aqueous solutionthan either of the hydrophilic first comonomer or second comonomer alone(or treated similarly as the polymeric composition).

Applications for the inventive compositions include their use incatheters, needles, sutures, stents and other implantable medicaldevices, contact lenses, root canal fillers, wound dressings, burndressings, tissue culture plates, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic showing (A) the radical polymerization ofP(VP-co-HEMA) and (B) quaternization of P(VP-co-HEMA)-HB.

FIG. 2 is graph of bactericidal results for surface testing ofP(VP-co-HEMA)-HB.

FIG. 3 is a graph of advancing and receding contact angles forP(VP-co-HEMA).

FIG. 4 is a graph of bactericidal results for testing ofP(VP-co-PEGMA1100).

DETAILED DESCRIPTION

In order to provide a more clear and consistent understanding of thespecification and claims, the following definitions are provided. Unlessdefined otherwise, all technical and scientific terms have the samemeaning as is commonly understood by one of skill in the art to whichthis invention belongs.

The term “monomer” refers to a relatively simple compound, usuallycontaining carbon and of low molecular weight, which can react to form apolymer by combining with itself or with other monomers.

The terms “polymer” and “polymeric composition” are used interchangeablyto denote a product of a polymerization reaction, and are inclusive ofhomopolymers, copolymers, terpolymers, etc.

The terms “polymerization” and “polymerization reaction” are inclusiveof homopolymerizations, copolymerizations, terpolymerizations, and thelike, and include all types of copolymerizations such as random, graft,block, and the like. In general, the polymers in the bactericidalcomposition on may be prepared in accordance with any suitablepolymerization process, including slurry polymerization, solutionpolymerization, emulsion polymerization, gas phase polymerization, andhigh pressure polymerization and the like.

The term “comonomer” refers to a monomer, copolymer, or polymer whichcan copolymerize with itself or with at least one different monomer,copolymer, or polymer in a copolymerization reaction, the result ofwhich can be a polymer, copolymer or polymeric composition.

The term “copolymer” refers to a polymer which can copolymerize withitself or with at least one different comonomer, polymer, or copolymerin a polymerization reaction or it can refer to a product resulting froma polymerization reaction of two comonomers. The copolymer may beidentified or named in terms of the monomer(s) from which the copolymeris produced.

The terms “corresponding comonomer,” “corresponding copolymer,” and“corresponding polymer” are used to relate comonomers, copolymers, orpolymers, respectively, sharing a common set of monomeric units betweene.g. distinct polymeric compositions. The common comonomers, copolymers,or polymer need not be identical in terms of the molecular weight(s) ormolar ratio(s) of commonly shared monomeric units.

The phrase “corresponding molecular weight” is used to relate molecularweight(s) of corresponding comonomers, copolymers, or polymers,respectively, in distinct polymeric compositions in which the commoncomonomers, copolymers, or polymers differ from one another by molecularweight(s) or commonly shared monomeric units within the correspondingcomonomer, copolymer or polymer.

The phrase “corresponding molar ratio” is used to relate molar ratio(s)of corresponding comonomers, copolymers, or polymers, respectively, indistinct polymeric compositions in which the common comonomers,copolymers, or polymers differ from one another by molar ratio(s) orcommonly shared monomeric units within the corresponding comonomer,copolymer or polymer.

The term “bactericidal” is used to interchangeably denote any one of thefollowing: (i) a comonomer, polymer, copolymer, polymeric compositionsuitably formulated to kill, reduce the growth, number, viability and/ormetabolic activity of one or more bacteria; (ii) a material, substance,medium, device, or area treated with a bactericidal comonomer, polymer,copolymer, polymeric composition so as to kill, reduce the growth,number, viability and/or metabolic activity of one or more bacteria.

The term “aqueous solution” refers to a solution in which water is thesolvent.

The term “medium” refers to a treatable material, treatable substance,treatable device, or treatable area in which “treatable” refers to acapacity to be rendered bactericidal by a bactericidal comonomer,polymer, or copolymer. A treatable medium may have a defined physicalform, but may include liquid (e.g., water, aqueous solution) or gaseousmaterials (e.g., air) also.

The phrases “significantly reducing the growth of bacteria” and“significantly reducing bacterial growth” are used interchangeably todenote one or more of the following conditions, including (i) acondition in which the metabolic activity of at least 50% of themicroorganisms of a particular type exposed to a treated medium isterminated or reduced compared to bacteria of that particular typeexposed to an untreated medium over a fixed period of time; (ii) acondition where there is 50% or less of one or more bacterial typespresent in and/or on a treated medium compared to the number of bacteriaexposed to an untreated medium; and/or (iii) a condition resulting whenone or more types of bacteria adhere 50% less to a treated mediumcompared to an untreated medium. The degree of bacterial growthreduction with respective to conditions (i)-(iii) may range from 50% togreater 99.9%.

The phrase “significantly bactericidal” denotes a comonomer, polymer,copolymer, composition, polymeric composition, material, substance ortreated area in which the bactericidal comonomer, polymer, copolymer,composition, polymeric composition, material, substance or treated areais suitably formulated to significantly reduce the growth, number,viability and/or metabolic activity of bacteria by at least 50%.

The term “biocompatible” refers to a material that is substantiallynon-toxic in the in vivo environment of its intended use, and that isnot substantially rejected by the patient's physiological system (i.e.,is non-antigenic). This can be gauged by the ability of a material topass the biocompatibility tests set forth in International StandardsOrganization (ISO) Standard No. 10993 and/or the U.S. Pharmacopeia (USP)23 and/or the U.S. Food and Drug Administration (FDA) blue bookmemorandum No. G95-1, entitled “Use of International Standard ISO-10993,Biological Evaluation of Medical Devices Part-1: Evaluation andTesting.” Typically, these tests measure a material's toxicity,infectivity, pyrogenicity, irritation potential, reactivity, hemolyticactivity, carcinogenicity and/or immunogenicity. A biocompatiblestructure or material, when introduced into a majority of patients, willnot cause a significantly adverse, long-lived or escalating biologicalreaction or response, and is distinguished from a mild, transientinflammation which typically accompanies surgery or implantation offoreign objects into a living organism.

A bactericidal polymeric composition of the present invention includes ahydrophilic first comonomer polymerized to a second comonomer, where thepolymeric composition is more soluble and/or more bactericidal in anaqueous solution than either of the first comonomer or the secondcomonomer alone. The polymeric composition of the present invention werefound to have unexpected hydophilizing and/or wettabiliy propertiesproviding enhanced bactericidal activity compared to either comonomeralone.

The second comonomer may be inherently bactericidal or it may berendered bactericidal after a subsequent step (e.g., polymerization)and/or chemical modification (e.g., quaternization) of alkyl groups.Where the polymeric composition is further modified by chemicalmodification, such as quaternization, preferably, the polymericcomposition is more hydrophilic and/or bactericidal than a similarlymodified (by e.g., quaternization) second comonomer alone.

Bactericidal comonomers or those capable of being rendered bactericidalare copolymerized to a hydrophilizing comonomer. Exemplary secondcomonomers for polymerization to a hydrophilizing comonomer may includea variety of vinyl monomers capable of free radical polymerizationand/or quaternization. Accordingly, these comonomers may include, butare not limited to, vinyl amines, such as N,N-dimethylvinylamine; allylamines; vinyl esters, such as vinyl acetate; alkyl acrylates; and vinylchloride. In a preferred embodiment, a pyridinium-type comonomer, suchas vinyl pyridine or 4-vinylpyridine, is quaternized afterpolymerization to a hydrophilizing comonomer.

The second comonomer composition may include or be chemically linked toa suitable bactericidal moiety, including, but not limited topolycationic species, polycationic derivatives or combinationstherefrom. Polycationic species may contain two or more quaternaryammonium groups with a molecular weight ranging from several hundredDaltons to a few hundred thousand Daltons. The quaternary ammoniumgroups may be part of a ring or they may be acyclic. Examples includebut are not limited to: polyionenes, poly(diallyldimethylammoniumchloride), dimethylamine-epichlorohydrin copolymers andimidazole-epichlorohydrin copolymers. Suitable bactericidal comonomersfor use in the present invention may include the quaternary ammoniumgroup-containing polymers disclosed in U.S. Pat. No. 4,482,680, whichare incorporated by reference herein.

Polycationic species may contain two or more amine groups. The aminegroups can be primary, secondary, tertiary, or mixtures thereof. Theamine groups may be part of a ring or they may be acyclic. Examplesinclude but are not limited to: polyethyleneimines, polypropyleneimines,polyvinylamines, polyallylamines, polydiallylamines, polyamidoamines,polyaminoalkylmethacrylates, polylysines, and mixtures thereof.

The polycationic species may also be a modified polyamine with at leastone amine group substituted with at least one other functional group.Examples include ethoxylated and alkoxylated polyamines and alkylatedpolyamines. Other suitable bactericidal comonomers or those that may berendered bactericidal may be identified and/or used in accordance withthe applications and objectives set forth in the specification andclaims.

Quaternization may be carried out using alkylating agents, including butnot limited to alkyl halides (such as hexyl bromide), alkyl sulfonates,alkyl mesylates, alkyl tosylates, or other alkylating agents possessinga suitable leaving group. Quaternization reduces self-polymerization ofthe bactericidal comonomer upon polymerization with the hydrophilizingcomonomer. Quaternization may confer increased bactericidal activity andis typically carried out after polymerization, since quaternizedpolymers are unpolymerizable.

Quaternized alkyl groups and/or other cationic chains may be attractedto and/or promote interaction and penetration negatively chargedbacterial cell walls on account of their lipophilic nature. Alkyl chainlengths of quaternizing agents and overall hydrophilic/lipophilicbalance may affect bactericidal activity of the polymeric compositionsof the present invention. Accordingly, these variables may be modifiedto optimize or improve bactericidal activity of the polymericcompositions.

Hydrophilizing comonomers of the present invention confer increasedwettability or hydrophilicity to one or more surfaces of the polymericcomposition in aqueous solutions, including water. Preferably, thepolymeric composition is more wettable than a bactericidal comonomer ora comonomer rendered bactericidal by quaternization, such aspoly(4-vinylpyridine). Suitable hydrophilizing monomers or copolymers,may include, but are not limited to, ethylene glycol (ethylyene oxide);polyethylene glycol derivatives, including poly(ethyleneglycol)methacrylate (PEGMA), poly(ethyleneglycol) acrylate, and vinylpolyethylene glycol; vinyl acetate; poly(vinyl alcohol); vinylpyrrolidone and poly(vinyl pyrrolidone); vinyl pyrrolidinone andpoly(vinyl pyrrolininone); vinyl oxazoline and poly(vinyl oxazoline);vinyl foramide and poly(vinyl foramide); hydroxyalkyl acrylates andhydroxyalkyl methacrylates, such as hydroxyethyl methacrylate (HEMA) andhydroxyethyl acrylate; methacrylamide; acrylamide and methacrylamidebased monomers, such as acrylamide, N,N-dimethyl acrylamide, N-ethylacrylamide, N-isopropyl acrylamide, and hydroxymethyl acrylamide;monomers containing one or more of the following functional groups:hydroxy, amino, ammonium, ether, carboxylate, amide, and sulfoamidegroups; and combinations or copolymers thereof. polyvinyloxazolines

Hydrophilic polymeric compositions and methods for hydrophilizingpolymeric materials, including the use of high energy treatments, aredisclosed in U.S. Pat. Appl. No. 20050008839, the contents of which areexpressly incorporated by reference in their entirety, also may be used.

Preferably, the hydrophilizing comonomer is biocompatible. Standardassays may be utilized to evaluate biocompatibility, including but notlimited to viability/cytotoxicity mammalian cell assays and the like.Representative hydrophilizing comonomers or copolymers includehydroxyethylmethacrylate (HEMA) and poly(ethyleneglycol) methacrylate(PEGMA).

HEMA is widely used in biomedical applications and devices, mostprominently soft contact lenses. HEMA, with 37.8% water per weight, istypical of hydrogels. Preferably, the molar ratio of HEMA comonomer inthe polymeric composition is equal to or greater than about 90 to 1.

PEGMA is a biocompatible polymer which possesses several importantproperties, such as good solubility in both organic and aqueous media,low toxicity, immunogenicity and nonbiodegradability.

Preferably, the molar molecular weight of PEGMA comonomer in thebactericidal composition is equal to or greater than 300, morepreferably between about 300 and about 2000, including but not limitedto 1100. Preferably, the molar ratio of PEGMA comonomer in the polymericcomposition is equal to or less than about 10 to 1; equal to or lessthan about 25 to 1; equal to or greater than about 75 to 1; equal to orgreater than about 95 to 1; equal to or greater than about 99 to 1.

Hydrophilicity or wettability can be evaluated by any suitablemethodology known in the art, including contact angle testing andtensionometry testing. Contact angle testing of polymeric compositionsmay be carried out by dip coating microscope slides in solutions withcopolymer dissolved in chloroform and methanol and obtaining contactangle measurements using e.g., a Ramé-Hart Advanced Goniometer. Contactangles may be characterized as advancing or receding, the differencebeing whether or not the angle is taken when moving onto a dry surfaceor moving off a wet surface. Advancing angles may be used for surfaceenergy determinations, receding angles for characterizing other surfacecharacteristics.

Polymeric bactericidal compositions may be rendered hydrophilic byengineering them to have advancing contact angles with water of lessthan or equal to about 90 degrees, preferably less than or equal toabout 45 degrees, more preferably less than or equal to about 30degrees, less than or equal to 15 degrees after 30 seconds of spreading.

The disclosed bactericidal compositions are suitably formulated tosignificantly reduce the growth, number, viability and/or metabolicactivity of bacteria. A bactericidal composition may be formulated tosignificantly reduce bacterial growth from a treated medium by a factorof at least 50%. Further, a bactericidal composition may be formulatedto significantly reduce bacterial growth from a treated medium by atleast 60%, by at least 70%, by at least 80%, by at least 90%, by atleast 95%, by at least 99%, or by at least 99.9%.

The bactericidal composition may be applied as a coating to at least oneportion or surface of a medium or medical device, including but notlimited to catheters, needles, stents, and other implantable medicaldevices. Various methods may be used to apply the comonomers orbactericidal polymers as a coating to the surface of the medical device.Suitable methods for applying coatings may include, but are not limitedto the methods disclosed in U.S. Pat. No. 5,509,899 and U.S. Pat. No.6,221,425, the contents of which are expressly incorporated by referencein their entirety.

Comonomers may be applied to a surface and subsequently polymerized.Alternatively, the bactericidal polymer composition may be applieddirectly to the surface of the medical device. In particular, one ormore comonomers or bactericidal polymers may be combined with water andsprayed onto the medical device. Alternatively, the medical device maybe dipped into a solution containing the bactericidal polymer. Thecomonomer or bactericidal polymer may be present in the solution in anamount from about 50% to about 98% by weight, particularly from about70% to about 90% by weight, and applied to the surface of the medicaldevice.

The viscosity of the monomeric or polymeric solution can be adjusteddepending upon the particular application and circumstances. In general,when dipping the medical device into the solution, higher viscositieswill cause more of the bactericidal polymer to remain on the surface ofthe device. Thus, if thicker coatings are desired, the viscosity can beincreased. The viscosity of the solution can be increased by minimizingthe amount of water in the solution. Additionally, thickeners, such as apolyacrylamide, can be added to the solution. The viscosity of thesolution may also be increased by partially polymerizing the monomer.

In another example, the present invention provides methods for renderinga material or area bactericidal. In a further example, the presentinvention provides a method for killing or significantly reducing thenumber of bacteria on a material or area treated with a bactericidalcomposition of the present invention.

Accordingly, in one example, a bactericidal composition of the presentinvention is applied to a medium or medical device in an amountsufficient to kill or significantly reducing the number of bacteria inor on the treated medium compared to an untreated medium. In a furtherexample, a bactericidal composition according to the present inventionis applied to a medium or medical device in an amount sufficient to killat least one bacterium or significantly reduce bacterial growth comparedto an untreated medium.

The bacteria may be Gram-positive or Gram-negative. The bactericidalcomposition may be is included in or coated onto a catheter, stent,implantable medical device, contact lens, root canal filler, or wounddressing. The treated medium may include natural or synthetic materials,implantable devices, or bodily surfaces. The treated medium may becontact with an aqueous environment, such as water or the inside of apatient or other vertebrate organism. Alternatively, the treated mediummay be contact with air or air and/or air borne bacteria in an externalenvironment or an enclosed bodily organ, such as lung.

Biocompatibility may be evaluated by any suitable methodology known inthe art, including biocompatibility tests set forth in InternationalStandards Organization (ISO) Standard No. 10993 and/or the U.S.Pharmacopeia (USP) 23 and/or the U.S. Food and Drug Administration (FDA)blue book memorandum No. G95-1, entitled “Use of International StandardISO-10993, Biological Evaluation of Medical Devices Part-1: Evaluationand Testing.” In addition, any of the viability/cytotoxicity assaysknown to those of ordinary skill in the art may be used to evaluate lackof toxicity for normal human cells.

In a further example, the present invention provides a method foridentifying a polymer having suitable bactericidal activity. In thismethod, a hydrophilizing first comonomer may be polymerized to a secondcomonomer and a bactericidal polymeric composition is formed. Thebactericidal polymeric composition may be applied to a medium to form afirst treated medium and the medium may be separately treated with thesecond comonomer used in the first treated medium. The first treatedmedium and the second treated medium may be separately contacted with aplurality of bacteria. Whether the first treated medium is morebactericidal than the second treated medium may be determined.

In a further example, a first polymeric composition and a secondpolymeric composition differing by molecular weight with regard to oneor more corresponding comonomers may be separately applied to a mediumand tested to identify a polymeric composition having improvedbactericidal activity.

Alternatively, a first polymeric composition and a second polymericcomposition differing by molar ratio of their corresponding comonomersmay be varied and may be separately applied to a medium and tested toidentify a polymeric composition having improved bactericidal activity.

In the above disclosed methods, a given polymeric composition may berendered bactericidal by quaternization after polymerizing thehydrophilizing first comonomer to the second comonomer. Accordingly, thequaternized polymeric composition would be deemed suitable for use in abactericidal composition if a medium containing or treated with thequaternized polymeric composition is more hydrophilic and/orbactericidal than the same medium containing or treated with thequaternized second comonomer alone.

Bactericidal activity may be evaluated using any suitable testingmethodology used in the art, including, but not limited to,luminescence, optical density, or microscopic evaluation of bacterialgrowth or viability of coated and/or stained microscopic slides, platesor cultures.

The following examples illustrate features in accordance with thepresent invention, and are provided solely by way of illustration. Theyare not intended to limit the scope of the appended claims or theirequivalents.

EXAMPLES

1. Radical Polymerization and Quaternization. Copolymers possessingsuitable bactericidal properties and a suitablehydrophilicity/biocompatibility profile were obtained using aquaternized polymeric composition synthesized from 4-vinylpyridine and abiocompatible, hydrophilic comonomer, such as hydroxyethylmethacrylate(HEMA) or poly(ethyleneglycol) methacrylate.

Copolymers were synthesized by radical copolymerization with AIBN asinitiator. The reactants were stirred at 70° C. for 48 hours underflowing N₂ to prevent oxidation. As the monomer contents were varied,the AIBN proportion was held constant to a massic ratio VP+PEGMA:AIBNequal to 22:1. To investigate the effects of hydrophilization, sevendifferent compositions of VP with PEGMA300, PEGMA 1100 and HEMA weresynthesized, containing a molar percentage of VP of 10, 25, 50, 75, 90,95 and 99.

Copolymers were quaternized with a 3-fold excess of hexyl bromide (HB)in a mixture of chloroform and methanol by reflux for 48 hr. They wereprecipitated in hexane, recovered and dried under vacuum. A schematic ofthe radical polymerization and quaternization process can be seen inFIG. 1.

Synthesis of P(VP-co-HEMA), P(VP-co-PEGMA300) and P(VP-co-PEGMA 1100)was followed with FTIR and NMR. Spectroscopy showed that the synthesiswas successful and that the quaternization went to near completion andthat the resultant products were relatively pure after work-up.

VP, HEMA and PEGMA were purchased from Sigma Aldrich Co. (Milwaukee,USA). To avoid polymerization through heat or light, these monomers wereinhibited with hydroquinone (HQ), 4-Methoxyphenol (MEHQ), and2,6-di-tert-butyl-4-methylphenol (BHT) respectively. The HQ and MEHQinhibitors were removed by means of trap to trap while BHT was purifiedfrom PEGMA by column chromatography on silica gel (70-270 mesh)stationary phase.

2. Contact Angle and Bactericidal Testing. To evaluate wettability orhydrophilicity, contact angle tests were conducted by dip coatingmicroscope slides in solutions with copolymer dissolved in chloroformand methanol. Contact angle measurements were obtained on a Ramé-HartAdvanced Goniometer.

Bactericidal tests were performed with a small quantity of the bacteriaEscherichia coli O157:H7 in which the lux gene was added forluminescence, which provides a measure of metabolic growth or activity.A sample was taken from a culture and placed in contact with the coatedslides, by means of a pipette. The intensity of the bioluminescence wasrecorded as a function of time for two hours with a photomultipliertube. Reduced bioluminescence correlates with enhanced bactericidalactivity.

3. Bactericidal activity of P(VP-co-HEMA). The results of thebactericidal tests on quaternized copolymers of VP and HEMA are shown inFIG. 2. An initial increase of intensity is observed in the control, dueto the fast growth of the bacteria, called blooming. After approximately19 minutes, the intensity starts decreasing as the bacteria start todie. PVP-HB, known to kill bacteria, prevents blooming, as reflected bythe fact that the intensity never increases by more than 1 percent. Theintensity starts decreasing after only 7 minutes. Since this is muchearlier than the control, the death of the bacteria can be attributed tothe properties of the polymer. An uninterrupted blooming is observed fora slide coated with PHEMA, and the number of bacteria has quadrupledafter two hours, following a lag-log behavior. This indicates that PHEMAby itself is not bactericidal.

P(VP-co-HEMA)-HB 95/5 and P(VP-co-HEMA)-HB 90/10 exhibited enhancedbactericidal activity compared to PVP-HB alone. The luminescencerecorded for P(VP-co-HEMA)-HB 99/1, is similar to, but slightly lessthan that observed for PVP-HB alone. Accordingly, this copolymer, havingone molar percent HEMA, displays properties similar to PVP-HB alone.However, a slide coated with P(VP-co-HEMA)-HB 99/1 kills bacteria fasterthan one coated with PVP-HB.

The wettability of dry, vitreous HEMA-based materials was studied bycontact angle measurements. The results for both advancing and recedingangles are given in FIG. 3. Contact angle measurements showed anincrease in hydrophilicity provoked by the copolymerization. The surfaceenergy was found to be minimal for P(VP-co-HEMA) at 90/10 and slightlyhigher for P(VP-co-HEMA)-HB 99/1. This corresponds to the bactericidalbehavior of the polymers and suggests that the wettability plays asignificant role in the polymer's effectiveness. Being a hydrogelmonomer, HEMA hydrophilizes the copolymer.

Although not wishing to be bound by theory, it is believed that couplinghydrophilization to bactericidal activity in the polymer facilitatesenhances bacterial killing, in part because of the water-loving natureof bacteria: a hydrophilic growth medium is better able to supportuptake and killing by a hydrophilized bactericidal polymer compared toan unhydrophilized bactericidal polymer. Moreover, it is believed thatthe bactericidal polymers are electrostatically attracted to thebacterial cell wall whereby lipophilic side chains insert into thebacterial cell membrane, disrupting it so that holes form therein.

In P(VP-co-HEMA)-HB 90/10, the wettability effect is particularlyevident. This polymer exhibits a more optimal bactericidal activity,reflected in the fact that all bacteria were killed in 30 minutes. Thisfurther illustrates that that a slide coated with P(VP-co-HEMA)-HB 90/10copolymer is significantly more bactericidal than pure PVP-HB.

4. Bactericidal activity of P(VP-co-PEGMA). The bacterial growthbehavior for copolymers with PEGMA1100 can be seen in FIG. 4. Comonomerratios of 90/10, 25/75, and 10/90 exhibited enhanced bactericidalactivity compared to PVP-HB alone. Extremely high bactericidal activitywas seen with ratios of 99/1, presumably due to the large fraction of VPand improved wettability from PEGMA1100. Copolymers with ratios rangingfrom 95/5 to 50/50 displayed bacterial results similar to PVP-HB.

P(VP-co-PEGMA1100)-HB 25/75 and 10/90 displayed a surprisingly highantibacterial activity. Although counterintuitive, this fact can haveseveral explanations. The molecular weight of P(VP-co-PEGMA1100)-HB10/90 is much higher than other copolymer formulations of this system.This could increase bactericidal activity, because the copolymerpossesses more alkyl tails to traverse the bacterial membranes. Theenhanced water wettability of the polymer may enable the polymer tobetter dissolve in and/or surround the bacteria in an aqueous medium, soas to facilitate more efficient bacterial killing.

PPEGMA300 (graph not shown) alone does not kill bacteria and actuallyimproves growth due to its biocompatibility and hydrophilicity. Theimproved biocompatibility and hydrophilicity is carried over into theP(VP-co-PEGMA300) copolymers with ratios from 0/100 to 50/50 therebyimproving bacterial growth. However, for ratios greater 50/50,bactericidal activity was observed. The optimum balance betweenspreading and VP content was found to be 75/25, in which half thebacteria were killed in the first 15 minutes. Overall, the bactericidalbehavior of the PEGMA300 based polymers were reduced compared toPEGMA1100 based polymers.

PEGMA1100 has a significantly larger PEG size than PEGMA300. A smallerfraction of PEGMA 1100 is thus necessary to hydrophilize P(VP-co-PEGMA1100). However, even for some similarly hydrophilized polymers, thePEGMA 1100 materials exhibit superior bactericidal activity, possiblydue to the enhanced protein resistance imparted by longer PEG chains inthe polymers.

The enhanced bactericidal activity exhibited by the HEMA and PEGMAcopolymers appears to result from enhanced wettability in aqueoussolutions, allowing the polymer to better surround and/or gain access tothe bacteria, so as to enhance bacterial killing.

5. Cytotoxity of P(VP-co-PEGMA). A viability/cytotoxicity assay may beused to evaluate biocompatibility of the bactericidal polymers formammalian cells. In particular, FIG. 5 shows that an exemplarybactericidal PEGMA 1100 copolymer is non-toxic to mammalian cells.Corneal epithelial cells were seeded onto polystyrene culture plates inphosphobuffered saline solution (PBS; pH 7.2) at a density of 3,500cells/cm² for 24 hrs at 37° C. The cells were co-incubated for 4 hrs.with quaternized P(VP-co-PEGMA 1100) copolymer or PPEGMA control polymerin PBS at a concentration of 2.5 mg/ml, along with a PBS negativecontrol media.

Live cells were distinguished from dead cells using a fluorescence-basedLIVE/DEAD viability/cytotoxicity assay system (Molecular Probes,Invitrogen Detection Technologies). The assay system includes twoprobes, calcein AM, a fluorogenic esterase substrate producing a greenfluorescent product in live cells having intracellular esteraseactivity, and ethidium homodimer-1, a high-affinity, red fluorescent dyeonly able to pass through and stain the compromised membranes of deadcells. FIG. 5 plots the fraction of dead epithelial cells as a functionof added bactericidal polymer or polymer control. As shown in FIG. 5,treatment of epithelial cells with the bactericidal P(VP-co-PEGMA)polymer did not exhibit a statistically significant level of epithelialcell killing over that of the PEGMA polymer or PBS negative controls.

It is to be understood that the above-described polymers and methods fortheir use are merely representative embodiments illustrating theprinciples of this invention and that other variations in the polymersor methods, may be devised by those skilled in the art without departingfrom the spirit and scope of this invention. The foregoing detaileddescription and accompanying drawings have been provided solely by wayof explanation and illustration, and are not intended to limit the scopeof the appended claims. Many variations in the presently preferredembodiments illustrated herein will be apparent to one of ordinary skillin the art, and remain within the scope of the appended claims and theirequivalents.

1. A polymeric composition comprising: a hydrophilic first comonomerpolymerized to a second comonomer to form a polymeric composition, wherethe polymeric composition is more hydrophilic than either of the firstcomonomer or the second comonomer alone and/or where the polymericcomposition is more bactericidal than either of the first comonomer orthe second comonomer alone.
 2. The composition of claim 1, where thehydrophilic first comonomer comprises hydroxyethylmethacrylate.
 3. Thecomposition of claim 1, where the hydrophilic first copolymer comprisespoly(ethyleneglycol) methacrylate.
 4. The composition of claim 1, wherethe second comonomer comprises polycationic species, polycationicderivatives or combinations therefrom.
 5. The composition of claim 1,where the second comonomer comprises a plurality of quaternary ammoniumgroups.
 6. The composition of claim 1, where the second comonomercomprises quaternized poly(4-vinylpyridine).
 7. A method for killingbacteria or rendering a medium bactericidal comprising: providing apolymeric composition comprising a hydrophilic first comonomerpolymerized to a second comonomer, where the polymeric composition ismore hydrophilic than either of the first comonomer or the secondcomonomer alone and/or where the polymeric composition is morebactericidal than either of the first comonomer or the second comonomeralone; applying the polymeric composition to a medium to form a treatedmedium, where the polymeric composition is applied in an amountsufficient to kill at least one bacterium or significantly reducebacterial growth in or on the treated medium compared to an untreatedmedium.
 8. The method of claim 7, where the polymeric composition isapplied as a coating to at least one surface of the medium.
 9. Themethod of claim 7, where the treated medium is in contact with anaqueous environment.
 10. The method of claim 7, where the treated mediumis in contact with air.
 11. The method of claim 7, where the treatedmedium is included in or coated onto a catheter, stent, implantablemedical device, contact lens, root canal filler, or wound dressing. 12.The method of claim 7, further comprising the step of contacting thetreated medium with bacteria, where the treated medium comprises thepolymeric composition in an amount sufficient to kill at least onebacterium or significantly reduce bacterial growth in or on the treatedmedium compared to an untreated medium.
 13. The method of claim 12,where the treated medium is formulated to kill or significantly reducethe growth of Gram-positive bacteria.
 14. The method of claim 12, wherethe treated medium is suitably formulated to kill or significantlyreduce the growth of Gram-negative bacteria.
 15. A method of identifyinga polymeric composition suitable for use in a bactericidal compositioncomprising: a) providing a first comonomer, where the first comonomer issoluble in an aqueous solution; b) providing a second comonomer, wherethe second comonomer is bactericidal or capable of being renderedbactericidal; c) polymerizing the first comonomer in step (a) to thesecond comonomer in step (b) to form a polymeric composition; d)treating or applying the polymeric composition in step (c) to a mediumto form a first treated medium; e) separately applying a comonomer fromstep (a) or step (b) to the medium of step (d) to form a second treatedmedium; f) separately contacting the first treated medium and the secondtreated medium with a plurality of bacteria; and g) determining whetherthe first treated medium is more bactericidal than the second treatedmedium, where the polymeric composition is suitable for use in abactericidal composition if the first treated medium is morebactericidal than the second treated medium.
 16. The method of claim 15,where each comonomer from step (a) and step (b) is separately applied tothe medium of step (d) to form a second treated medium and a thirdtreated medium, respectively, where the polymeric composition issuitable for use in a bactericidal composition if the first treatedmedium is more bactericidal than each of the second and third treatedmediums.
 17. The method of claim 15, where the molecular weight(s) ofone or more more monomers in the first comonomer in the first polymericcomposition of the first treated medium is modified compared to thecorresponding molecular weight(s) of one or more monomers in a secondpolymeric composition of a fourth medium, such that the fourth treatedmedium is more bactericidal than the first treated medium.
 18. Themethod of claim 15, where a molar ratio(s) of one or one or moremonomers in the first comonomer in the first polymeric composition in afirst treated medium is modified compared to the corresponding molarratio(s) of one or more monomers in a second polymeric composition of afourth medium, such that the fourth treated medium is more bactericidalthan the first treated medium.
 19. The method of claim 15, where thesecond comonomer is quaternized after the second comonomer ispolymerized to the first comonomer.
 20. The method of claim 15, wherestep (g) comprises a luminescence assay, optical density determinationor microscopic determination.